Ton

Structure
The Ton system comprises of the triumvirate TonB/ExbB/ExbD inner membrane complex.

Function
The Ton proteins are involved in the uptake of vitamin B12 and chelated-iron into the cell, and the system as a whole is known to be an energy-transducing system. Each of the three proteins involved have their separate role. For more information, see the respective pages for TonB, ExbB and ExbD.

The Ton system can be exploited by group B Colicins {see Colicin for more details) which include :
 * Colicin 5
 * Colicin 6
 * Colicin 7
 * Colicin 8
 * Colicin 9
 * Colicin 10
 * Colicin Ia
 * Colicin Ib
 * Colicin B
 * Colicin D
 * Colicin M
 * Colicin V
 * Colicin Js
 * Colicin Y

It is interesting to note that the name 'Ton' comes its resistance to the T1 phage.

Interaction of Ton proteins
Like in the Tol complex, the Ton system proteins interact with each other :
 * 1) the transmembrane domain of TonB interacts with both ExbB and ExbD, which contribute to the stability of the protein and support the TonB-dependent active transport across the outer membrane.
 * 2) ExbB and ExbD interact with each other, which has been suggested to play a part in the mechanism of energy transduction